High auto-ignition temperature explosive



May 2, 1961 s. D. RQLLE HIGH AUTO-IGNITION TEMPERATURE EXPLOSIVE Filed Sept. 10, 1959 To Vacuum Pump g IN V EN TOR. SYLVAN D. ROLLE AT TORNEY United States Patent HIGH AUTO-IGNITION TEMPERATURE EXPLOSIVE Sylvan D. Rolle, Philadelphia, Pa., assignor to the United States of America as represented by the Secretary of the Army Filed Sept. 10, 1959, Ser. No. 839,266

1 Claim. (Cl. 52-15) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein maybe manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.-

This invention relates to explosives suitable for use in percussion primers or in the operation of various kinds of load devices such as aircraft escape systems and the like. Its purpose is to provide explosives which withstand a relatively high temperature during storage and burn, upon their ignition, with suflicient rapidity to insure the utilization of their fuel potential.

Propellants presently suitable for the operation of load devices generally have auto-ignition temperatures such that they will not withstand a few hours exposure to temperatures above 300" or 400 F. Protection against these temperatures has been attempted by insulating the cartridge or applying a heat sink. These expedients have the disadvantage that they render the device unduly bulky.

It has been proposed in connection with primers to form the explosive of laminae of sulfur and potassium chlorate separated by a temperature resistant membrane. While this provides a satisfactorily high auto-ignition temperature, its inhomogeneity slows down the propagation of the initial reaction to a point where the potential effectiveness of the explosive is not realized.

The aforesaid explosive consists of elements which are in or may be reduced to the form of granules and are capable individually of withstanding relatively high temperatures. In accordance with the present invention, the auto-ignition temperature of the explosive is raised by coating the granules of one or more of the elements with a material providing a suitable temperature resistance. This coating consists of lead or other substances which prevent reaction to storage temperatures but respond to the firing of the explosive by melting quickly and facilitating propagation of the reaction throughout the whole 'material of the explosive.

The invention will be better understood from the 2,982,642 Patented May 2, 1961 following description when considered in connection with the accompanying drawing and its scope is indicated by 1 the appended claim.

The single figure of the drawing shows a granule coating device consisting of a base 10 and a bell jar 11 resting on this base to form a chamber within which are a plurality of granules 12. This chamber has an outlet 13 which is connected to a vacuum pump (not shown). Entering the chamber through insulated and gas tight fittings are a pair of electrical leads 14 which have their inner ends connected together through a lead wire 15. At the outer terminals of these wires is a power source, shown as a battery 16, and a switch 17. This device is well known and is included herein merely to facilitate an understanding of the present invention.

The coating of the granules 12 is effected in two steps. First the bell jar is evacuated. Then the switch 17 is closed to vaporize the lead wire 15 after which this vapor settles on the granules. In order to ensure complete coverage of the granules, they may be placed on a screen or vibrated slightly during the coating process.

If the explosive is black powder consisting of sulfur, carbon and potassium nitrate, the auto-ignition temperature is sufiiciently raised by coating the potassium nitrate granules and forming them into a homogeneous mass with the sulfur and carbon granules. When this explosive is fired, the heat of reaction melts the barrier material and the usual propagation of flame by chain reaction ensues. If the explosive is a primer mixture of sulfur and potassium chlorate the same procedure is applicable. In these and other cases, the auto-ignition temperature of the explosive is raised to a desired value without reducing the burning rate of the explosive. Insofar as is now known, the above-identified method is the only one whereby the explosive hereinafter claimed may be produced.

I claim:

1. In a method of increasing the auto-ignition temperature of an explosive selected from the group consisting of carbon-sulfunpotassium nitrate and sulfur-potassium chlorate, the steps comprising granulating each constituent of said explosive, placing at least one of the References Cited in the file of this patent UNITED STATES PATENTS Ellsworth July 15, 1930 Colbert et a1. Got. 5, 1948 

1. IN A METHOD OF INCREASING THE AUTO-IGNITION TEMPERATURE OF AN EXPLOSIVE SELECTED FROM THE GROUP CONSISTING OF CARBON-SULFUR-POTASSIUM NITRATE AND SULFUR-POTASSIUM CHLORATE, THE STEPS COMPRISING GRANULATING EACH CONSTITUENT OF SAID EXPLOSIVE, PLACING AT LEAST ONE OF THE GRANULATED CONSTITUENTS OF SAID EXPLOSIVE IN A CHAMBER, EVACUATING CHAMBER OF AIR, VACUUM DEPOSITING A FILM OF LEAD AROUND EACH OF THE CHAMBERED GRANULES AND COM- 